The present invention relates to a method of manufacture of a barrage unit. More particularly, but not exclusively, the present invention relates to a method of manufacture of a barrage unit including the steps of blowing fibres of a fibrous material into a chamber where they are mixed with an absorbent crystalline material before being deposited on a liner. In a further aspect the present invention relates to a barrage unit manufactured by the method according to the invention.
Barrage units which absorb water are known. PCT/GB2008/000185 discloses a barrage unit having a core comprising a mixture of an absorbent fibrous material and an absorbent crystalline material. Such barrage units are typically used as a defense against flooding or as a blast defense system.
Such known barrage units are typically manufactured by mixing together the absorbent fibrous material and absorbent crystalline material by hand. Alternatively, the two are laid down in layers. This approach has a number of drawbacks however. Firstly the barrage units tend to shed the absorbent crystalline material. When this gets wet it can form a low friction layer on the ground which can be dangerous. More significantly, this method of manufacture can result in an uneven distribution of the absorbent crystalline material, either at the time of manufacture or due to movement of the barrage unit thereafter. The uneven distribution can cause the crystals of the absorbent crystalline material to clump together when absorbing water. This reduces the rate of water uptake of the barrage unit and possibly also the total amount of water the barrage unit will absorb. It can also cause the barrage unit to expand in an unpredictable manner and form an undesirable final shape.
The method of manufacture of a barrage unit according to the invention seeks to overcome the problems of the prior art.